Seraph of the End, Vol. 6

The only thing standing between humans and complete slavery to vampires is their tenacity and Cursed Gear. Yuichiro has the first in droves, but to increase the amount of power he can draw from the demon inside his cursed sword, he enters a coma-like state to thin the barrier between human and demon. His power boost can come none too soon as the vampire queen reveals her plans to annihilate the human resistance.

Volume 6 of the Seraph of the End manga series by Takaya Kagami.